Researchers led by Jenny Alongi of Italy’s Politecnico di Torino dunked cotton, polyester and a polyester-cotton blend into a liquid formula of powdered milk proteins called caseins, which are key to making cheese. The researchers found that the phosphate-rich proteins extinguished fires set on the fabrics, slowing the spread of blazes by 40 to 70 percent.

Upon burning, caseins may release acids, such as phosphoric acid, that for...